The majority of the world population is infected by the herpesvirus, human cytomegalovirus or HCMV. Infection occurs through exchange of body fluids and the initiation of a lytic replication cycle within the host. Afterwards, HCMV enters a latent state with periods of reactivation. This ability to go latent results in a lifelong persistent infection. Infection causes severe disease in immunosuppressed individuals and is the number one cause of viral-mediated congenital birth defects. In addition, long term infection of otherwise healthy individuals is linked to cardiovascular disease and immunosuppression in the elderly. Upon infection of a host cell, viruses must overcome the cell's innate ability to prevent viral replication. Our long-term goal is to determine how HCMV proteins manipulate cellular proteins in order to establish a permissive environment for replication. Recently, we have identified a network of virus-host protein interactions linking the regulation of mTOR signaling pathways with chromatin remodeling factors. One of these proteins is HCMV pUL29/28. We observed using a proteomic approach that pUL29/28 interacts with the tumor suppressor protein, p53, along with deacetylase complexes and the HCMV protein, pUL38. The overall objective of this application is to determine the function of HCMV pUL29/28 within this network of interactions. Our central hypothesis is that pUL29/28 facilitates regulation of p53-dependent viral and cellular promoter activation through altering chromatin structure and interacting proteins. Expression of the cellular tumor suppressor protein p53 is up regulated during HCMV infection. Under these conditions, p53 induces viral gene expression but not cellular gene expression. In general, activation of p53 does not result in induction of every one of the p53-inducible promoters. Depending on the situation, p53 "chooses" the promoters it activates to best accommodate the situation at hand. Our preliminary data suggest a model in which pUL29/28 is functioning to control p53 promoter choice. We will achieve our objective by completing the following three aims. AIM 1. Role of pUL29/28 and pUL29/28-binding proteins in different steps of HCMV replication. We will test the hypothesis that the function of pUL29/28 in gene expression versus DNA replication depends upon distinct subsets of interactions. AIM 2. pUL29/28-mediated changes in posttranslational modifications of histones and nucleosome remodeling at responsive promoters. We will test the hypothesis that pUL29/28 regulates gene expression and DNA replication by modifying chromatin structure. AIM 3. Direct regulation of p53 within infected cells. We will test the hypothesis that pUL29/28 functions, in part, by altering posttranslational modifications of p53 and p53 interacting proteins during infection. Our proposed studies will provide insight into the complex yet coordinated mTOR signaling pathways and p53-regulated events during HCMV infection. PUBLIC HEALTH RELEVANCE: HCMV infection is associated with a diverse range of pathologies within the population. The focus of this proposal is to identify the role of viral proteins in regulating complex cellular stress responses. Cells initiate these responses to stop infection and are key pathways for antiviral pharmaceutical discovery.